Aneurysms are enlargements or bulges in blood vessels that are often prone to rupture and, therefore, may present a serious risk to a patient. Aneurysms may occur in any blood vessel and are of particular concern when they occur in the cerebral vasculature or the aorta.
There is some concern about aneurysms occurring in the aorta, particularly those referred to as aortic aneurysms. Abdominal aortic aneurysms (AAAs) are classified based on their location within the aorta as well as their shape and complexity. Aneurysms that are found below the renal arteries are referred to as infrarenal abdominal aortic aneurysms. Suprarenal abdominal aortic aneurysms occur above the renal arteries, while thoracic aortic aneurysms (TAAs) occur in the ascending, transverse, or descending part of the upper aorta.
Infrarenal aneurysms are the most common, representing about 70% of all aortic aneurysms. Suprarenal aneurysms are less common, representing about 20% of the aortic aneurysms. Thoracic aortic aneurysms are the least common and often the most difficult to treat.
Among the macroscopic shape and size classifications is the most common form of aneurysm known as “fusiform,” where the aortic wall enlargement compared to its normal diameter extends about the entire aortic circumference. Less common aneurysms may be characterized by a bulge on one side of the blood vessel attached at a narrow neck. Thoracic aortic aneurysms are often aortic wall dissecting aneurysms caused by hemorrhagic separation in the aortic wall, usually within its medial layer.